package com.itheima.demo;

import java.util.Scanner;

public class Demo003 {
    public static void main(String[] args) {
        //求1-100的和;
        Scanner sc = new Scanner(System.in);
        int i = sc.nextInt();
        int result = getSum(i);
        System.out.println(result);
    }

    private static int getSum(int i) {
        if (i == 1) {
            return 1;
        } else {
            return i + getSum(i - 1);
        }
    }
}
